The present invention relates to an apparatus for measuring the density of vertebrae or the like, in which a portion to be inspected (for example, vertebrae) of a subject or the like can take a plurality of predetermined positions between a gamma ray source and a detecting area.
The inventors of the present invention have developed an apparatus for measuring the density of an object having a small transmission factor. In this apparatus, a gamma ray source is used for emitting gamma rays within a predetermined solid angle from a fixed point. The gamma rays transmitted through a subject to be measured are collimated by a collimator. The collimator is situated a predetermined spatial distance along an axial line from the gamma ray source corresponding to the solid angle, and includes a number of capillaries directed to the fixed point. A scintillator is disposed close to the collimator, and photomultipliers are arranged close to each other with their photocathodes facing the scintillator. A position-operating integrated circuit estimates incident positions on the basis of an incident unit when light of the scintillator impinging onto the photomultipliers is temporally separated. The circuit integrates an incident frequency at every incident position, thereby obtaining data relating to density of an object having a small transmission factor by irradiating the object with gamma rays for a predetermined time.
The following problems arise when data as to density of vertebrae of a subject is to be obtained. Vertebrae are considered to be the most important bodily portion in measurement of bone density. Around the lumbar vertebrae, there are arteries in which sedimation of calcium may occur, and calcium absorbs gamma rays. In the case where measurement is performed from the front of a subject, there is no problem of simultaneous transmission through bisymmetrical bones. However, there is a serious problem in that arteries may be superimposed upon bones. If measurement is performed from the side of the subject, arteries are less likely to be superimposed upon bones, so that the measurement can be carried out with no problem even in the case of a subject in which calcium has settled in the arteries. Therefore, it is desirable to be able to measure the subject from a plurality of directions.
In order to keep a subject at a predetermined position during photographing or the like by exposure to gamma rays, a holder (for example a chair) has been used to fix the position of the subject. Although this enables a subject to be kept at a predetermined position, the conventional apparatus is not suitable for performing measurement from different angles.